87 lines
3.6 KiB
C++
87 lines
3.6 KiB
C++
/*
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* Copyright (C) 2014 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "java_lang_ref_Reference.h"
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#include "nativehelper/jni_macros.h"
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#include "gc/heap.h"
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#include "gc/reference_processor.h"
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#include "jni/jni_internal.h"
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#include "mirror/object-inl.h"
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#include "mirror/reference-inl.h"
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#include "native_util.h"
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#include "scoped_fast_native_object_access-inl.h"
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namespace art {
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static jobject Reference_getReferent(JNIEnv* env, jobject javaThis) {
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ScopedFastNativeObjectAccess soa(env);
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const ObjPtr<mirror::Reference> ref = soa.Decode<mirror::Reference>(javaThis);
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const ObjPtr<mirror::Object> referent =
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Runtime::Current()->GetHeap()->GetReferenceProcessor()->GetReferent(soa.Self(), ref);
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return soa.AddLocalReference<jobject>(referent);
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}
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static jboolean Reference_refersTo0(JNIEnv* env, jobject javaThis, jobject o) {
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if (kUseReadBarrier && !kUseBakerReadBarrier) {
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// Fall back to naive implementation that may block and needlessly preserve javaThis.
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return env->IsSameObject(Reference_getReferent(env, javaThis), o);
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}
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ScopedFastNativeObjectAccess soa(env);
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const ObjPtr<mirror::Reference> ref = soa.Decode<mirror::Reference>(javaThis);
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const ObjPtr<mirror::Object> other = soa.Decode<mirror::Reference>(o);
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const ObjPtr<mirror::Object> referent = ref->template GetReferent<kWithoutReadBarrier>();
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if (referent == other) {
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return JNI_TRUE;
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}
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if (!kUseReadBarrier || referent.IsNull() || other.IsNull()) {
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return JNI_FALSE;
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}
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// Explicitly handle the case in which referent is a from-space pointer. Don't use a
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// read-barrier, since that could easily mark an object we no longer need and, since it
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// creates new gray objects, may not be safe without blocking.
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//
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// ConcurrentCopying::Copy ensure that whenever a pointer to a to_space object is published,
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// the forwarding pointer is also visible. We need that guarantee to ensure that if referent
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// == other and referent is in from-space, then referent has a forwarding pointer. In order to
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// use that guarantee, we need to ensure that the forwarding pointer is loaded after we
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// retrieved other. Hence this fence:
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atomic_thread_fence(std::memory_order_acquire);
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// Note: On ARM, the above could be replaced by an asm fake-dependency hack to make
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// referent appear to depend on other. That would be faster and uglier.
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return gc::collector::ConcurrentCopying::GetFwdPtrUnchecked(referent.Ptr()) == other.Ptr() ?
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JNI_TRUE : JNI_FALSE;
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}
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static void Reference_clearReferent(JNIEnv* env, jobject javaThis) {
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ScopedFastNativeObjectAccess soa(env);
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const ObjPtr<mirror::Reference> ref = soa.Decode<mirror::Reference>(javaThis);
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Runtime::Current()->GetHeap()->GetReferenceProcessor()->ClearReferent(ref);
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}
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static JNINativeMethod gMethods[] = {
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FAST_NATIVE_METHOD(Reference, getReferent, "()Ljava/lang/Object;"),
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FAST_NATIVE_METHOD(Reference, clearReferent, "()V"),
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FAST_NATIVE_METHOD(Reference, refersTo0, "(Ljava/lang/Object;)Z"),
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};
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void register_java_lang_ref_Reference(JNIEnv* env) {
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REGISTER_NATIVE_METHODS("java/lang/ref/Reference");
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}
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} // namespace art
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